Method of coating fragile metal foils



Jan. 6, 1942'. R. s. 'REYNOLDS METHOD 0F COATING FRAGILE METAL FoIiLskv kFiled Aug. ll, 1938 M MC, #mi Q ylwld; f TORNEY v `lNvl-:NTOR Hchard Re Y excessive.

Patented Jan. 6, 1942 i FOIL Richard Samuel Reynolds, Richmond, "Va.,' as-f 'f signor to Reynolds Research Corporatiom Richmond, Va., alcorporation'of Delaware '-4 Appuoauop August 11,1938, serial' No. 224,296 Y l 2 claims.

This invention specifically relates to a new and improved method of coating thin metal foils, particularly aluminum foil, with various liquid filming materials such as cellulose derivatives of the type of cellulose acetate and cellulose nitrate, Vistanex, a polvmerizedstraight chain petroleum hydro-carbon, rubber, or rubber derivatives of the type of chlorinated rubber and rubber hydrohalides, and various other solutions of lacquerlike substances suitable for being dissolved in a more or less viscous solution with a volatile solvent capable of forminga film upon the evaporation of the solvent, and in its larger aspects the invention contemplates a new andf improved method of generally processing metal foils.

Heretofore thin metal foils in their processing, particularly processing involving coating the same with vcellulose acetate lms or like iilms, have been ordinarily processed in the form of continuing bands or webs: however, due to the lack oi.' tensile strength, the .bands or webs of the thinner foils, especially foils under .001" thick,

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the second layer/is coatedand dried and the tvvo4 ing continuous.

layers of foil each having a coating, are then separated and separately wound, the Process be- It will be understood that single or double coatings may be appliedto either one lor more layers of foil by methods involving my invention, and the accompanying drawing illustrates diagrammatically the manner in which the present invention may be practised, .but it is to be expressly understood that the drawingis for the purpose of illustration only and is not to be considered as limitingl the invention in any way whatever.

In the drawing: f

Fig. 1 is a diagrammatic view of an apparatus which Imay be employed in the practise of my have often ruptured and broken, making the cost of processing such bands or webs of thinner foils It has been widely recognized that if the factor of breakage could be overcome it would be cheap and economical -to utilize the thinner coated metal foils for a variety of purposes, because the coatings materially add to the tensile strength of the foil and also fill in or cover microscopic holes or perforations therein, the

, coated thin metal foils being particularly eilicient as a packaging or wrapping medium.

Therefore, it is an object of my, invention to process, and to process particularly by coating, a. layer of thin andfragile metal foil which is backed up and supported by at least one other invention.-

Fig. 2 is a cross-section of two layers'of foil whichhave'been coated with cellulose acetate in accordance with my invention.

In these figures a spool of foil 'I0 comprises two layers I2 and I4 of coincidently wound thin fragile metal foil, preferably aluminum foil, which layers are preferably mutually co-extensive and of equal gauge. 'I'he layers I2 and Il are led over guide roller I6 and top layer I2 is coated with a solution of cellulose acetate having a volatile solvent, thecoating I8 preferably being applied by extruding the solution from a" pressure hopper in accordance with methods described in the patent application of- Dn E. L.

Mack and Earle H. Morse, Serial No. 148,382,

layer of metal foil, preferably of equal gauge, o

and to commence such processing by having two or more layers of foil coincidently .wound on a ing as they do the stresses and strains of processing together supplement one anothers tensile strength, thus giving the double-layered stock more tensile strength than possessed by a single layer.

, It is a further object of this invention to coat foil in two layers according to the method described above, in which the layers are fed from a coincidently wound spool, so that the top layer may be first coated and dried and then the double positions of the layers become reversed, the bottom layer becoming the top layer, aftrwhich spool so that the layers may be processed in web form as a unit and so that the layers., encounterlayered web led around guide rolls so that the now Patent No. 2,175,125, granted October 3, 1939,

' entitled Method and apparatus for forming. lms

and nlm coatings; if desired well known milercoatiig or spray-'coating vmethods could be femployed. The coatinggland the two layers' of` foil I2 "and Il' are then-"led v'to drier 2Il where the volatile' solvent of' the coating solution'ds j dried out. The triplicate layers I2,II and I8- areA then led past guide rollers 22 and 24 so that the foil layers I2 and I4 are in reverse positionv and a cellulose acetate coating'28 is then applied to foil layer Ilby means of extrusion pressure hopper zaino coating 2s beingy driodin drierV 30, after which the two coated layers of foil I2 and I4 are led over guide roller 32, separatedand each wound separately on spools 3l and 36,'

Those skilled in the art will 'recognize lthe economy and eiiciency of processing fragile foils in the manner described above. particularly adapted for rthin fragile metal foils of a thickness ranging from .00023"-.001", but can be used to minimize breakage of the web in foils The method is cf'resr thickness. s The method n advantageous in processing or coating various metal foils and is especially desirable for processing extremely thiny aluminum foils with a single coating| usually of a cellulose derivative type which gives increased strength to the foil and iills in any microscopic holes, and the method may also bevused where it isdesir'ed to double coat layersy of -foil with a primary coating such asvistanex. and

then over-coat the primary coating witha coating of preferably a cellulose derivative'type;

Various modifications and. combinationsv of l vav rious features of the present invention as heretofore set out by illustrative examples will nowl occur to those skilled in theart from the draw-Q` ing and description, and certain procedures described may be replaced by other procedures and Having described the invention. what n claimed 1. The method of coating thin fragile relatively air impervious metal foil of a thickness ranging from .00023.001" which includes the steps of feeding two or more layers of foil in back to back relation from a coincidentally wound roll.V

coating 'at leastonelayerwith a nlm forming material having a volatile solvent and drying the r wound roll, coating one layer and then reverscertain features used without other features withf out departing from the spirit ofthe invention. Reference is therefore to be had tov the claims K i for g dnnitiqnof saidvinvention.

ingthe layers and coating the other layer and drying the coatings while maintaining the layers in back to back relation, and then separating the 20 coatedglayers.

RICHARD'SAMUEL REYNOLDS. 

